Infrared Detectable MoS2 Phototransistor and Its Application to Artificial Multilevel Optic-Neural Synapse.

Layered two-dimensional (2D) materials have entered the spotlight as promising channel materials for future optoelectronic devices owing to their excellent electrical and optoelectronic properties. However, their limited photodetection range caused by their wide bandgap remains a principal challenge in 2D layered materials-based phototransistors. Here, we developed a germanium (Ge)-gated MoS2 phototransistor that can detect light in the region from visible to infrared (λ = 520-1550 nm) using a detection mechanism based on band bending modulation. In addition, the Ge-gated MoS2 phototransistor is proposed as a multilevel optic-neural synaptic device, which performs both optical-sensing and synaptic functions on one device and is operated in different current ranges according to the light conditions: dark, visible, and infrared. This study is expected to contribute to the development of 2D material-based phototransistors and synaptic devices in next-generation optoelectronics.